Dark Sectors at the Fermilab SeaQuest Experiment

Transcription

1 Dark Sectors at the Fermilab SeaQuest Experiment Stefania Gori University of Cincinnati New Probes for Physics Beyond the Standard Model KITP April 9, 2018

2 Dark sectors Dark matter (DM) exists! The stronger and stronger bounds from DM direct detection experiments may suggest that DM couples to SM with couplings weaker than weak The Standard Model (SM) is highly non-minimal DM needs lighter mediators Dark sector! (in principle) mediated by the Z or Higgs boson Already some evidence? DM self interactions 2/20

3 Mediating DM interactions The most simplified models Dark sector (DM + ) DM DM Secluded scenario SM SM SM SM More hidden to direct detection and collider Pospelov, Ritz, Voloshin, Bounds from cosmology: CMB, Neff 3/20

4 Long lived particles Depending on the strength of the connection between the SM and the dark sector, mediators can decay promptly back to the SM be long lived be stable 4/20

5 Long lived particles Depending on the strength of the connection between the SM and the dark sector, mediators can decay promptly back to the SM be long lived be stable Curtin, Essig, SG, Shelton, ~ Lower bound from thermalization DM DM most of the exp. bounds Evans, SG, Shelton, /20

6 Fixed target experiment program e/p DM or SM See eg. Dark sector community report, Beam Dump Decay volume Detector 5/20

7 Fixed target experiment program e/p DM or SM See eg. Dark sector community report, Beam Dump Decay volume Detector Past It corresponds to ~ O(100 ab -1 ) data! Present Future (*) (*) talk by J.Feng 5/20

8 Fermilab intensity frontier 120 GeV high-intensity proton beam Fermilab has a very high intensity proton beam! Proton Improvement Plan to get very high intensity (PIP, PIP II, PIP III) Final goal: ~2 MW of proton beam power (now ~700 KW) 6/20

9 Fermilab intensity frontier 120 GeV high-intensity proton beam Fermilab has a very high intensity proton beam! Proton Improvement Plan to get very high intensity (PIP, PIP II, PIP III) Final goal: ~2 MW of proton beam power (now ~700 KW) The SeaQuest (nuclear physics) experiment 5% main injector beam Dump Decay volume Detector 6/20

10 SeaQuest in a nutshell 1. Compact geometry Sensitivity to slightly displaced dark particles with d > 5m 2. KMAG separating even very forward muons ( ) Identification of very light dark particles/squeezed spectra 7/20

11 SeaQuest in a nutshell 1. Compact geometry Sensitivity to slightly displaced dark particles with d > 5m 2. KMAG separating even very forward muons ( ) Identification of very light dark particles/squeezed spectra 3. A bit of history previous runs (since 2012) dedicated to prompt μ April 2017: installation of displaced di-muon trigger 3 x POT collected in 5 running days Approved: physics run for ~10 18 POT by 2019 Work in progress: proposal for installation of ECAL (from the Phenix experiment) 7/20

12 SeaQuest in a nutshell 1. Compact geometry Sensitivity to slightly displaced dark particles with d > 5m 2. KMAG separating even very forward muons ( ) Questions for this talk Physics-case for the ECAL? Future runs with larger luminosities? Identification of very light dark particles/squeezed spectra What is the reach for dark photons, dark matter models, dark scalars, axions, Berlin, SG, Schuster, Toro, /20

13 Visible displaced signatures Fiducial regions Signatures Di-electrons (resolved & not resolved) Mesons Di-photons 1. (5-6)m 2. (5-9)m 3. (5-12)m Backgrounds for electron signatures The (5-6)m region has negligible background The largest decay region will probably have backgrounds. Experimental studies needed! We will show the reach corresponding to 10 signal events (MET) Luminosity POT (approved luminosity) POT (luminosity accumulated by MiniBooNE) 8/20

14 Dark photon models 1. Minimal dark photon model 2. Inelastic Dark Matter (IDM) See also talk by A.Berlin on SIMPs Berlin, Blinov, SG, Schuster, Toro, /20

15 A huge dark photon production if we take the 120 GeV Fermilab proton beam: Berlin, SG, Schuster, Toro, bremsstrahlung meson decay POT) 10/20

16 A huge dark photon production if we take the 120 GeV Fermilab proton beam: Berlin, SG, Schuster, Toro, bremsstrahlung meson decay POT) Generically larger rates than at electron fixed target experiments 10/20

17 1. High acceptance for minimal A High acceptance for boosted particles 11/20

18 The reach for the minimal A model Berlin, SG, Schuster, Toro, slightly displaced LHCb, POT POT (*) (*) decay regions: (5-6)m, (5-9)m, (5-12)m See Gardner, Holt, Tadepalli, for the muon reach as well 12/20

19 Comparison with future experiments FASER: Feng et al., POT NA62: CERN-EPFL-Korean theory institute POT SHiP: Alekhin et al., Berlin, SG, Schuster, Toro, /20

20 2. Inelastic DM Inelastic DM (IDM) models were initially proposed to explain the DAMA anomaly, while being consistent with Dark Matter direct detection bounds from CDMS Tucker-Smith, Weiner, The only relevant interaction is inelastic: 2-component Weyl spinors with opposite charge under U(1) The elastic piece is very small : Two states close in mass: Easy to get it small since it is a U(1) breaking effect 14/20

21 High-intensity probes of IDM IDMs are rather hidden to direct detection experiments Also CMB constraints are relaxed The prime avenue to probe IDM is at high intensity experiments? (see, however, Bramante et al., ) with Copiously produced at fixed target experiments Non-resonant decays 15/20

22 High-intensity probes of IDM IDMs are rather hidden to direct detection experiments Also CMB constraints are relaxed The prime avenue to probe IDM is at high intensity experiments? with Copiously produced at fixed target experiments Non-resonant decays Displaced decays 15/20

23 fixed target experiments Relic line Good coverage from past experiments for sizable mass splittings ( ) (in gray) see also Izaguirre et al /20

24 fixed target experiments Relic line Good coverage from past experiments for sizable mass splittings ( ) (in gray) Babar (inv.) not detected E137 (dec.) SLAC 20 GeV electron beam see also Izaguirre et al electrons from decay LSND (dec.) Los Alamos 800 MeV proton beam visible Bjorken et al. (1988) 16/20

25 fixed target experiments Relic line Less coverage from past experiments for smaller mass splittings ( ) (in gray) POT POT (5-6)m (5-9)m (5-12)m From darker to lighter see also Izaguirre et al POT (5-6)m, no KMAG The SeaQuest acceptance remains relatively high even for smaller mass splittings ((5-12)m fiducial region!) 16/20

26 fixed target experiments Relic line Less coverage from past experiments for smaller mass splittings ( ) (in gray) see also Izaguirre et al The SeaQuest acceptance remains relatively high even for smaller mass splittings ((5-12)m fiducial region!) 16/20

27 More broadly, Additional production mechanisms of dark particles? what type of searches (beyond e + e - ) can be carried over by the SeaQuest experiment in the future? Is there some upgrade we need? Scalars, axions, 17/20

28 Leptophilic scalars These scalars are not copiously produced from standard mechanisms BUT huge production of (relatively energetic) muons muon S e + e - 18/20

29 Leptophilic scalars These scalars are not copiously produced from standard mechanisms BUT POT POT huge production of (relatively energetic) muons muon S e + e - NA64-μ and FNAL-μ experiments proposed in Chen, Pospelov, Zhong, /20

30 Opportunities for axions huge production of (relatively energetic) photons POT POT photon a Backgrounds for photon signatures? few more meters of iron? 10 events, (7-8)m 19/20

31 Conclusions & Outlook Past, present & future fixed target experiments play a crucial role in testing interesting dark sector models A special role can be covered by Fermilab: SeaQuest (nuclear physics) experiment obvious advantage: Existing experiment! Minimal dark photon & dark scalar; Inelastic DM; axions (and Strongly-interacting DM) models can be broadly explored Additional models that SeaQuest can explore? (Particle) physics case? 20/20

32 Info about KMAG, IDM KMAG 10 signal events with POT with or without KMAG For our SeaQuest experimental colleagues: is the search without KMAG feasible? backgrounds? Backup

33 IDM acceptance at SeaQuest Berlin, SG, Schuster, Toro Backup

34 Dark scalars mixed with the Higgs At SeaQuest, scalars produced from the decay of heavy mesons: Scalars decaying to Kaons (small region of parameters) pions (backgrounds from?) electrons (typically small BR) muons (backgrounds?) 10 events, (7-12)m, inclusive decays Backup

35 Computing the efficiency at SeaQuest Total efficiency= For the minimal dark photon model: (and not! ) mean boost Berlin, SG, Schuster, Toro Backup

36 Indirect detection of IDM CMB constraints: coannihilation No significant constraint The DM candidate in IDM models can be thermal and below 10 GeV! Backup

37 Experimental program for WIMPs EXO Evans, SG, Shelton, Z-mediated, g~0.1 make it CMB, Dwarf galaxies, Cosmic rays, weak shake it Backup

38 Direct detection of IDM Direct detection signals are suppressed even for EW-scale DM Hall, Moroi, Murayama, loop suppressed dominant process larger recoil energy Data is not analyzed! Proposal: extend Xenon and Tungsten experiment analysis to high recoils data Bramante, Kribs, Fox, Martin, Backup

39 The WIMP next door Even in more pessimistic scenarios, there is a lower bound on the DM-SM interaction strength. Dark matter can reach the measured relic density via its interactions with the dark sector: Dark Dark Nevertheless, to achieve thermal contact between the SM and the dark sector, a minimum interaction strength is required: This bound will depend on the equilibration temperature Coupling Evans, SG, Shelton, Backup

40 Fixed target experiment program e/p DM or SM See eg. Dark sector community report, Beam Dump Decay volume Detector Past Present Future and many more Generically higher mass reach visible visible Past Present Future Other experiments to probe dark sector models? Backup

41 From nuclear to particle physics SeaQuest started in 2010 as a nuclear physics experiment Nuclear physics goal of the experiment: 3-dimensional proton tomography in momentum space through the precise measurement of Drell-Yan production. More in particular: understanding the origin of the nucleon spin Non-vanishing sea angular momentum distribution? The experiment can also be used for particle physics! Recent (April 2017) installation of a displaced trigger Searches for displaced dark sectors decaying after the dump In the near future, possibility of inserting a EMCAL between Station III and Station IV sensitivity to electrons A particle physics program to be written! Backup